PERFORATIONS OF MARINE ANIMALS. 59 
stances—Russian talc, paraffin varnish, oil of tar, various kinds 
of paint, and by carbonising (by burning) the surface of the 
wood ; but none of these methods met with their confidence. 
Impregnation of the wood was next tried with sulphate of 
copper, sulphate of iron, acetate of lead, calcium chloride, oil of 
tar, and creosote. The latter alone, and only when thoroughly 
carried out, was found to be useful; and at the present moment 
this, sheathing in copper, and the studding of the timber with 
broad-headed nails (scupper-nails) are the only reliable methods 
adopted in the Netherlands. And yet creosoted timber is not 
always safe, for Dr. Gwyn Jeffreys found it attacked in Sweden. 
Somewhat recently an American has recommended that a cylin- 
drical excavation round the core of logs of wood should be filled 
with a special cement, impenetrable to Teredo. It would be 
difficult, however, to adopt this on a large scale. 
While the Dutch, French, and other Commissions have thus 
done material service in regard to the best means for protecting 
timber from the attacks of various borers, the subject is by no 
means exhausted. On the contrary, it would form a fitting one 
for modern research at the Marine Laboratories. 
In the foregoing remarks only a brief résumé has been given 
of the kinds of marine animals which by the extent of their per- 
forations materially affect submerged timber and other solid 
substances. In conclusion, however, it is well to draw attention 
especially to the fact that this ceaseless boring in wood is not an 
unmitigated evil, even though Mr. Brunel had not received a 
hint from Teredo in forming the Thames Tunnel. The masses 
of timber swept seawards by many foreign rivers would prove a 
serious impediment to navigation if the marine borers did not 
slowly but surely accomplish their dissolution. In the same 
way floating timber and the relics of many a ship and boat in 
the depths of the sea are disposed of. Fortunately the extensive 
use of iron and steel in shipbuilding now renders the ravages of 
the borers in wood less prominent. Moreover, vast numbers of. 
shells are broken down by boring sponges, annelids, boring alge,* 
and other forms, and ultimately are either altogether dissolved 
or deposited as shell-gravel. Further, this increase of animal 
life —both larval and pelagic, and adult and sedentary—is every- 
* Bull. Amer, Mus. Nat. Hist. xxv. pp. 323-332, 1902. 
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